The typical modern city utilizes hundreds of miles of large diameter concrete pipe in its sewage collection system. As the city grows or improves its services, there is frequently the need to tear up streets and roadways to install new or larger sewer lines. Deep trenches are dug and concrete pipes several feet in diameter are installed. These new lines may extend several miles in length and their installation constitutes an extensive project in terms of the time and expense involved. Because of the interference with traffic and with the conducting of area businesses, it is important that the project be completed in as short a time as possible.
In the early application of concrete pipe for this purpose, the pipe sections were pre-cast at a fabricating facility and then transported to the point of installation. The hauling and installation of such large and heavy concrete pipes was difficult and expensive because the pipe sections had to be handled by heavy machinery. The hauling, distribution and installation of the pipes was also time consuming and added to the length of time that a given roadway had to remain torn up or blocked off.
It was then recognized that a more cost effective and time effective approach was to cast the concrete pipe in place. Such a pipe-casting machine is described in U.S. Pat. No. 3,252,198.
This machine substantially met the basic need for reducing the time and expense involved in the installation of the sewage lines, but the machine did not rise to its full potential because it was not self-propelled. This was a major disadvantage because a heavy tractor had to be made available to move the machine along. This was especially inconvenient because the deep trench and the earth removed from it constituted formidable obstacles in the areas over which the tractor had to be driven. Just having the tractor on hand for this purpose was also a significant expense.
The present invention is an improvement over the earlier machine of U.S. Pat. No. 3,252,198, the improvement comprising an inexpensive mechanism added to the machine to render it self-propelling.